There has been proposed a Micro-electromechanical system (MEMS) element including a mechanically movable unit. For example, the MEMS element can be applied to devices, such as a pressure sensor, a variable capacitor, and a micropump.
For example, in the case that the MEMS element is used as the pressure sensor, the MEMS element includes a fixed electrode and a movable thin-film dome (movable electrode). The pressure sensor measures a pressure at that time by detecting the capacitance (electrostatic capacitance) between the movable thin-film dome and the fixed electrode according to the pressure outside of the dome.
At this point, a large movement is generated in a central portion of the thin-film dome while a small movement is generated in an end portion. Therefore, the end portion of the thin-film dome does not contribute to the capacitance change between the thin-film dome and the fixed electrode too much compared with the central portion. In other words, only the central portion of the thin-film dome contributes to the capacitance change. As a result, the capacitance change between the thin-film dome and the fixed electrode is small for the external pressure, and the pressure sensor has poor sensitivity.
In the MEMS element, there is a demand to enhance the sensitivity as the pressure sensor to improve reliability.